Broken router bits - bad bits or operator error?

[Rich Engelhardt]

I made a Thein seperator today.
I used a shop made tramel, a PC 690 - w/1/4" collet - and a Ryobi 1/4" straight bit to cut the circular top out of 3/4" borg birch plywood.

I was only taking about 1/16" cuts w/each pass & going counterclockwise.
I heard a "CHA-CHINK" sound like I'd hit a knot or something, but, otherwise the router seemed to be cutting normally.
When I finished the cut, I stopped the router to change depth & laying in the groove was half a chewed up router bit:eek: :confused:.

I just chalked it up to a cheap Ryobi bit and grabbed another one.

I finished the 3/4" top and moved on to the 1/8" bottom piece - same tramel - and changed the depth so I was taking off just a hair under 1/16".

I'd just about finished the cut, when "CHA-Chink" and another half broken bit.

When I seated the bit, I bottomed it out then backed it off just a bit - like I usually do.

What gives? Just crappy bits or am I doing something wrong?

[george wilson]

Possibly cheap Chinese router bit. Their HSS is usually on the brittle side,but is also pretty hard,a bit harder than the usual HSS. I've found this true in lathe tools and milling cutters. Ryobi seems to be a poorer than usual brand of tools in my experience. I don't buy their stuff anymore.

[pat warner]

You're doing everything right.
My guess is your fixturing is sloppy.
If ever, on this endeavor, the cutter is taking a full or fractional target depth cut it may damn well break the bit.
Whilst the cutter is in the shoals (<3/8") expect little adversity.
But whence >3/8" in depth and your fixturing or router allows a cut slightly off the pathway (even a 1/32") it can & will break a skinny cutter.
Does your fixturing allow the router to slosh on its trip or is it always tight such that it can not deviate?
Made these through slots (http://patwarner.com/images/mort_jig3.jpg) with a 1/4" x 2" flute! cutter at ~1/16"/pass, no problems.
Fixturing (http://patwarner.com/images/morticing_jig.jpg) will not allow the machine to swim.

[Larry Edgerton]

I ruined a piece I had a lot of hours in with a brand new CMT bottom bearing pattern bit. As soon as I touched the wood/pattern all heck broke loose, bit broke, and piece was ruined. Apon inspection I found that the bearing was machined off center about 20 thousands of an inch. CMT offered to replace the bit, but I just said no thanks and never bought one again.

So....Even what could be considered a good bit can have issues. I don't really consider Ryoba's very good bits, but in my shop I would not make that cut with a 1/4" bit, I would use a 1/2" bit. 1/4" bits develop a wobble far to easily, which progresses until you get a broken bit. I saw a video of a bit losing it, and in slow motion it is easy to see how they snap.

Larry

[david brum]

I've used a few Ryobi bits. While they aren't particularly sharp, I haven't had any disintegrate. I suspect some foreign metal or similar in the Borg plywood. It is notoriously cheap stuff, although I'll admit to using it myself. There was a photo on one of the forums a few years ago, where someone had cut some Borg ply and found a crushed basketball between the plies.

I've certainly seen some sparks while cutting the stuff down to size with a circular saw.

[Rich Engelhardt]

Does your fixturing allow the router to slosh on its trip or is it always tight such that it can not deviate?

Pat - I believe you nailed it. Thank you!
I did have some slop in the fixture. That would explain why the second bit broke so easily on the thinner stock. The first one, I chalked up to bad bit/maybe taking too deep a cut on the 3/4" stock.
The 2nd bit that snapped happened about 4 inches into the cut & making a very shallow pass.

George - The Ryobi bits are supposed to be carbide. LOL! Maybe - but - more like they hold the bit up after they make it and wave a picture of a carbide bit at it.
I try to avoid Ryobi stuff unless it's a lower price than Harbor Freight or a super good buy.

Larry - All I had was 1/4" bits. I'm still in the process of using up all my 1/4" bits and replacing them with 1/2" shank ones.

David - That was my first thought - that I'd hit some piece of metal.

[Myk Rian]

It's possible you overheated the bit by taking such shallow cuts, and too many of them.
Take 1/4" cuts and get the job done.

[scott spencer]

It could be a combination of things...hard to know. In general, Ryobi bits and blades aren't overly well regarded for quality or value. Whiteside, Infinity, Eagle America, Freud, CMT, Amana are all good bits that tend to cost more, but bits like MLCS, Grizzly, Price Cutter, Holbren, Woodline, Woodriver, Rockler, PC are all better quality usually at comparable prices to Ryobi (depending on sales).

[Jerome Stanek]

I've had a couple of Grizzly bits explode on me I never will buy another one. I use Onsrud, Vortex, Amana and Whiteside.

[Kent A Bathurst]

I've always had better results by cutting close to the line with a BS or jig saw, then finishing to the line with a router - haven't snapped bits this way, but I have when making the entire cut with a router [1"+ QSWO]. I'm pretty sure my bit problems were pilot error, though - probably too impatient and moving too fast. But still....

[Jim Foster]

Pictures would be good to see if possible. Any HSS cutting tool and laminated wood (like plywood) do not go well together IMO. Did the shaft break? Or did the cutting edge chip off? When you said the bit was straight, was the cutting edge straight or fluted or spiral? A spiral bit can walk off the router surprisingly easy when cutting too fast or a tough material if the spiral is going in the direction where it pulls chips up instead of down